1.5.1 Latches and Seal-in

• Latches are one function built into PLCs, but there are variations.

• Basically, latches allow one or more values to be frozen in time.

• This circuit is a seal-in because the output locks the inputs on. After power is removed the logic will default to off.

1.5.2 Shift Registers

• These allow values to be put into a ‘pipe-line’ where values are shifted through one at a time.